Digital Data Calls Feature

Description

2B Data

The combination of two data-bearing channels (B-channels) allows ISDN-BRI devices (such as desktop and group video systems with ISDN-BRI interfaces) to connect to a single MLX port and make full 128-kbps connections using ISDN NI-1 BRI or ISDN PRI B-channels, or make 112-kbps connections when T1 Switched 56 facilities are used.

For more information about 2B data, see the Data/Video Reference.

Devices used for 2B data must be connected to MLX jacks that are programmed as 2B data-capable. Devices that do not support 2B data should not be connected to ports programmed for 2B data.

The MLX extension numbers used to add 2B data capability must correspond to the adjunct extension number for the MLX telephone. By default, in a two-digit numbering plan, these adjunct extensions are numbered with the digit "7" preceding the two-digit extension number. If the MLX extension is 20, its corresponding adjunct extension is 720. In a 3-digit or Set Up Space numbering plan, the adjunct extension number is, by default, the main extension number plus 200. (For details, see System Renumbering.)

Once an MLX jack is correctly programmed, a 2B data-capable device properly connected to the jack should operate at the same data rate (up to 128 kbps) as an NI-1 BRI line connected directly to a Central Office.

2B data calls are really two calls, one for each B-channel. (Similarly, ISDN terminal adapters that connect to V.35 video systems must make and receive two calls in order to provide double the speed of a single digital call.)

Users can use any combination of PRI, NI-1 BRI, and T1 lines to obtain a 2B data connection. However, data transfer speeds are slower on T1 Switched 56 lines (56 kbps on each line). Because of potential speed and other conflicts, it is best to use the same type of facility for both calls that make up a 2B data call.
MERLIN MAGIX Integrated Systems can be connected to one another or to DEFINITY ECS or DEFINITY ProLogix Solutions systems in a private network. If the tandem trunks connecting the systems are PRI and two B-channels are available, 2B data digital calls between the systems can take place at 128 kbps. If the tandem trunks connecting the systems are T1-emulated tie data trunks and two channels are available, 2B data digital calls between the systems can take place at 112 kbps.

Topics

Description

	Primary Rate Interface
	T1 Switched 56 Lines
	Basic Rate Interface
	2B Data

At a Glance

Considerations & Constraints

System Programming

Applications

Telephone Differences

Feature Interactions